How do I rig each blade to fan out like an aperture lens?
Copy Rotation Constraint + Local Space

I would move the triangle's origin somwhere along the shortest edge.



Then assing to the object a Copy Rotation Constraint pointing to an empty.



We are only interested in copying the rotation on one axis, in this case the Z axis as the blades are in the XY plane.

Notice that we must also change the Rotation space as in the picture above to transfer the rotation of the empty to the object's Local space.

Then we can duplicate the object and control the individual rotation of all blades with the empty: